REPORT OF COMMITTEE ON OBSERVATORIES 5 1 



(3) To provide, through the construction of a large reflecting 

 telescope, for the investigation of various problems of stellar evolu- 

 tion, intimately related to solar work, which existing instruments 

 are inadequate to solve. 



It will be seen that the investigations here proposed may be grouped 

 in another way, viz., (i) those which relate to the sun's radiation, 

 mainly with reference to its effect upon the earth ; (2) those which 

 relate to the solar constitution, with special reference to the sun as 

 a typical star ; and (3) those which relate to the evolution of stars 

 like the sun from nebulae. 



There are many important reasons to recommend the establish- 

 ment of a solar observatory by the Carnegie Institution. Up to 

 about the year 1875 a large amount of information regarding the 

 phenomena of the sun's surface had been collected, partly through 

 the utilization of more and more powerful telescopes, and particu- 

 larly through the recent application of the spectroscope. But since 

 that time, for reasons not easily to be explained, comparatively few 

 important advances in the study of these phenomena have been 

 made ; verj^ little advantage has been taken of the great improve- 

 ment in telescopes and in spectroscopes during the intervening quar- 

 ter of a century. No other department of astrophysical research 

 has been equally neglected, and consequently in none is there such 

 an exceptional opportunity for great advances. Only one of the 

 twenty two refracting telescopes "of from 20 inches to 40 inches 

 aperture is regularly used for work on the sun, and with but two or 

 three exceptions the solar spectroscopes in use are little better than 

 those of a quarter of a century ago. Though such spectroscopes 

 are fairly well adapted for the statistical work in which they are 

 employed, they are wholly incapable of dealing with phenomena 

 easily within reach of such spectroscopes as are used in physical 

 laboratories. Even in the few cases in which important advances 

 in solar investigations have been made, partly through the inven- 

 tion and perfection of new instruments, the means available have 

 generally been inadequate to bring out the full powers of new 

 methods of research, and atmospheric disturbances have always 

 most seriously hampered observation. What is needed is an observ- 

 atory at some suitable mountain site, where atmospheric disturbances 

 are reduced to a minimum ; the development of special forms of 

 telescopes, particularly adapted to solar work, and the complete 

 utilization of the numerous improvements in spectroscopes and other 

 instruments for physical research which have been developed in the 



